1. Field of the Invention
This invention generally relates to engine heads and more particularly to inner surfaces of engine heads that provide improved performance.
2. Description of the Related Art
Many workers in the art have attempted to improve performance by changing shapes of combustion chambers and by attempting to channel flow within the combustion chambers. Of particular benefit is the evolution in shape of combustion heads from a generally hemispherical shape to a configuration that includes a squish band that provides a small clearance between the engine head and the piston in a radially outer region of the head when the piston is in a top dead center (TDC) position. A radially inner region may have a hemispherical and/or bathtub shape. This combination of squish band and hemispherical and/or bathtub shape has increased the turbulence that occurs during the compression part of the combustion cycle. The results include improved efficiency and reduced pinging.
Others have experimented with different shapes within the combustion chamber. Some have implemented these different shapes by changing the contour on the piston crown or by placing channels in the piston crown. In U.S. Pat. No. 6,237,579, Singh teaches placing channels in the inner surface of the engine head. Singh does so for the purpose of improving turbulence in the combustion chamber.
Cylindrical engine heads of the past have typically been formed on a lathe or cast. Some workers have actually polished the inner surfaces of engine heads to improve flow along these surfaces. Even those who have placed channels in the combustion chamber have attempted to keep the surfaces smooth.
A rate of flow that becomes turbulent during the compression portion of the combustion cycle is beneficial because it places more of the combustible gas in contact with the spark and flame front more quickly. Since it is difficult to control the propagation of the flame front, a more turbulent mixing brings the combustible gases to the flame front. In this way, more of the fuel and air gases are ignited at once, and more power output and more complete combustion occurs. Keeping the fuel atomized in the fuel air mixture has also been a concern, and increased turbulence has been seen as aiding in keeping more of the fuel in an atomized state. Even with the progress that has been made, the amount of control and direction of combustion in a combustion chamber is still limited.